I probably need a link to the specific extended solution you are talking about. But every extended flight solution I have seen uses the P3 smart battery as the central battery and manager, and, to be conservative, systems always seem to supplement around that. So, there may be two other 4s's running in parallel. But, there are a lot of possibilities. For example, wired correctly, two 2s's in series can be the exact equivalent of a 4s if the cell size (and design) is the same.
My big deal is to see if I can not only re-cycle these smart-battery controls, as that isn't even what initially motivated me. I want to see what happens when I take that tired DJI battery out, and put a fresh one in. Heck, one the same size, maybe one a little bigger. Maybe don't use the center cavity, and use the sides, and put two 2s's and wire in series as a 4s, a bigger 4s, but much lighter than anything we have tried... You get the idea... But will it work? That is the million dollar question..... I am beginning to repeat myself, aren't I
.... Ok, I will shut up....
Btw, the smart battery plays possum. In testing the pin-outs I generated a few sparks. After a while the thing stopped turning on for me. It looked about as dead as dead can be. I figured I messed it up. A few hours later it was good as new. Don't ever throw them away! I bet they were designed that way
